"Ethan Winer" ethan at ethanwiner dot com wrote in message
...
Rusty,

If done properly with enough horsepower you get perfect
results at ANY
point in the room.

I don't dispute that for a moment!

Now tell me how deconvolution can be used in a practical
product that can
solve real world acoustics problems in home theaters and other
listening

I just did.

Thanks. The math is way over my head, but I did glean this
nugget from one
of those referenced pages:

"However, in the above single- and multi-channel approaches,
the requirement
that the room impulse response needs to be identified first
renders the
solution not readily applicable to a real situation."

The real nugget comes a few sentences later..."Currently we are
investigating blind deconvolution techniques which use available
signals like speech directly rather than chirp-like artificial
probing signals and identify a room impulse response quickly.
Fast adaptation schemes for tracking a changing room impulse
response are also under current study and related issues will be
discussed in this talk. "

Basically their original method for acquiring the impulse
response was flawed so they have moved on to other techniques.
BTW, that link is 6-1/2 years old.

In article ,
Rusty Boudreaux wrote:
"George Deliz" wrote in
message
This sounds very interesting. How is this done in practice?
Are there products available that would allow an audiophile to
do this
and about how much would it cost?

I'm not aware of any commercial solution for the audiophile
market. The signal processing details are way beyond the
capabilities of the typical high-end company. This is hard
science, not snake oil. Since the audiophile market is so tiny I
bet we won't see this in consumer applications until mainstream
receivers support it via an ASIC or chipset developed elsewhere.

This is an important point that bears repeating. The total
audiophile market is SO tiny that any company with the financial
wherewithall to do heavy DSP development would not even notice
if the high-end market were to suddenly vanish without a trace.
The size of this market combined with the utter irrational
insanity of it along with its volatility makes it unattractive
for any serious development effort. Basically why should a
company bother trying to cater to a segment that might,
altogether, make up 1% of its potential business yet cost it
tens times it in the trouble it would generate?

There is no innovation in the high-end to speak of, there's
little real development of any sort, there's no scholarly
research, just blind and stumbling intuition, snake oil, magic
arts and mythology.

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

On Fri, 12 Sep 2003 00:18:46 -0500, "Rusty Boudreaux"
wrote:

"Ethan Winer" ethan at ethanwiner dot com wrote in message
...
If I'm missing something important, explain so I'll learn.
Don't just hit
and run. And explain How and What room correcting DSP can do,
not just say

Like Dick Pierce and others have said, deconvolution.

Measure the impulse response of a room, invert it, and convolve
with the incoming audio. If done properly with enough horsepower
you get perfect results at ANY point in the room.

I assume you imply the postscript ", but only at one point at a time, unless you
have an infinite number of signal reproduction chains", since the room's impulse
response will be different at each point. This is an important distinction, and
seems to be a point of dissention in this discussion.

Regards,
Tony (remove "_" from email address to reply)

Rusty,

I just did. [tell me how deconvolution can be used in a practical product
that can solve real world acoustics problems in home theaters and other
listening

No you didn't, and you're just playing games now. What you said was, "If
done properly with enough horsepower you get perfect results at ANY point in
the room."

Yes, any ONE point. The issue is removing room problems for more than one
point.

BTW, that link is 6-1/2 years old.

Well, YOU'RE the one who posted it!

--Ethan

Ethan Winer wrote:

Randy,

Is it not possible that a topic may be complex enough that one or two
usenet news postings won't even come close to describing it in enough depth
that one really understands it?

All I'm asking for is an explanation of the concepts, not for you to hold my
hand through a bunch of higher math. When someone truly understands an
advanced process, they should be able to explain the basics in plain
English.

Perhaps I am able but not willing. It takes a lot of time to attempt to
do this, and in the end you may find the person doesn't really care all
that much. I feel (as someone else stated) that the burden is on you to
go spend the time to discover the details if you're that interested.
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% % 'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr

In article ,
Ethan Winer ethan at ethanwiner dot com wrote:
Richard,

What I said was in direct refutation of YOUR claim of such variations at
70 Hz over a span of one inch.

Okay, I agree. Not one inch, but four inches.

70 Hz corresponds to a wavelength of 16 feet. 4 inches
corresponds to a 7.4 degree phase shift. Your assertion that
such variation occurs over a distance of 4 inches or 7.4 degrees
is an extraordinary claim contrary to the behavior of waves.
It's as simple as that. You have continually made wild
assertions, backpedalled, changed your tune and provided the
most sloppy and incomplete of "measurement" in an attempt to
"defend" your case.

I don't know why we're still arguing about this. I accept that deconvolution
can do amazing things for a single point in the room. What I do not accept
is that it's a practical solution, especially when conventional acoustic
treatment does a much better job over a much wider area and for much less
money. This is the real issue, not whether deconvolution works.

Well, sir, you have asserted that your treatments "do a much
better job," and if the data YOU presented about YOUR treated
room is ANY indication, then it does a LOUSY job.

Further, you have admitted you know NOHING about the basic
proinciples of decomvolution, so who ae you to make further
assertions about how it does or does not work?

Bill agreed with you guys that deconvolution is absolutely amazing. But he
also said he agrees with me that it's not a practical solution for room
acoustic treatment. In fact, the purpose of my visit there was to deliver
eight of my company's MiniTraps for him to try because he has severe
acoustics problems in his large living room home theater. That an expert in
the field of echo cancellation chooses conventional acoustic treatment tells
all.

Sir, we are simply not impressed with your story.

Consider this: explain to us how a trap which takes up very
small percentage of the total surface area of a reflecting
surface can change the effective absorbtion coefficient of that
surface by any more than a small percentage? Let's even assume
that your trap absorbs 100% of the energy impinging upon it,
please tell us how the VAST mojority of the energy, which does
NOT impinge upon it, is an any way affected?

It would seem that, by your own data, they are, in fact, deeply
ineffective. This is maybe one reason why "bass traps" are NOT
used by professional acoustic engineers in real acoustic
situations, rather they deal with the bulk acouctical properties
of the room rather than these magical "band aids" of yours.

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

"Ethan Winer" ethan at ethanwiner dot com wrote in message
...
that for the past five years he has headed development for a
company that
makes the EXACT type of DSP you and I have been discussing.

What's the company? If he's really the chief scientist I bet
I've met him.

He knows
everything about deconvolution and echo cancellation.
Everything. He codes

Everything?

Wow, I guess all future research in signal processing is over.
We just have to ask this guy.

He said it can absolutely do
everything you claim EXCEPT work over a range wider than a few
inches. Bill
told me that when the goal is to increase the range, the
corrections must be
relaxed - the compensating peaks and nulls are made less deep
and with a
lower Q, etc. - so the end result is a wider area of
correction, but with
reduced efficacy at all locations.

Well, the fact that he's explaining in terms as "compensating
peaks and nulls", "lower Q, etc." means that either he does not
grasp the concept of deconvolution or has not kept up with
current research.

Here's a hint - how many speaker locations does it take to
perfectly correct for the room at EVERY location?

In fact, the purpose of my visit there was to deliver
eight of my company's MiniTraps for him to try because he has
severe
acoustics problems in his large living room home theater. That
an expert in
the field of echo cancellation chooses conventional acoustic
treatment tells
all.

If he were indeed an expert in all things wave he'd be laughing
at the concept of Bass Traps. Decpetive marketing at best.
Snake oil at worst.

Rusty,

What's the company? If he's really the chief scientist I bet I've met
him.

Your address appears valid so I'll send you that via email. I'm not
comfortable dragging his name into this publicly.

Everything?

He is totally on top of the current state of the art.

the fact that he's explaining in terms as "compensating peaks and nulls",
"lower Q, etc." means that either he does not grasp the concept of
deconvolution or has not kept up with current research.

I didn't bring a tape recorder so I paraphrased. Gimme a break, okay? But he
did mention DSP correcting the peaks and nulls that occur in different
places in a room. You may feel that's a simplistic explanation, but Bill
knows my level and was right to put it in terms I can understand. If DSP
fixes room problems, and part of that is to reverse the peaks and nulls, why
do you criticize that explanation? And besides, that wasn't even meant as a
"grand explanation" of deconvolution anyway. It was just a way to explain
the trade-off between correcting a tiny part of a room perfectly or a larger
area less completely. Again, act like a human being and give me a freakin'
break. Instead of attacking me or Bill, why don't you address the actual
issues?

how many speaker locations does it take to perfectly correct for the room
at EVERY location?

I have no idea. Bill mentioned that one of his systems uses eight speakers
and eight mikes. The systems he designs are not meant for room correction in
hi-fi listening rooms, though they're related closely enough to use
identical technology.

If he were indeed an expert in all things wave he'd be laughing at the
concept of Bass Traps. Decpetive marketing at best. Snake oil at worst.

That's an astounding statement from someone who claims to be an audio
professional.

--Ethan

Richard,

Your assertion that such variation occurs over a distance of 4 inches or
7.4 degrees is an extraordinary claim contrary to the behavior of waves.

I measured 100 Hz, not 70, but I'm sure the results will be similar at 70
Hz. So you're still disputing my *measured* response variations? Have you
never played a sine wave in a room and walked around? It only takes a few
minutes.

explain to us how a trap which takes up very small percentage of the total
surface area of a reflecting surface can change the effective absorbtion
coefficient of that surface by any more than a small percentage?

Sure, easy. Bass traps work best in the room corners. Put them there, where
the bass frequencies focus, and you can absorb more than the equivalent
surface area would indicate. Also, the way my company's products are mounted
further increases their effective coverage. If you get a moment visit our
site - it's quite informative.

Do a dozen bass traps in a room solve all problems? No, of course not. You'd
have to cover literally every surface with material that's 100% absorbent at
all frequencies to achieve a perfectly flat response. But good bass traps
can transform a terrible room into one that's a pleasure to mix in, and they
can make a good room truly great. Practically speaking, acoustic treatment
cannot make every location in a room perfect, though I already told you I
had to hunt for a place in my studio having such deep nulls. The goal for
folks with a limited budget - pretty much everyone - is not necessarily
perfection, just to make the room good enough to mix in with confidence.

This is maybe one reason why "bass traps" are NOT used by professional
acoustic engineers in real acoustic situations

Tell that to all the professional recording engineers who love our products!

if the data YOU presented about YOUR treated room is ANY indication, then
it does a LOUSY job.

I have tried hard to engage in a meaningful discussion, and have been met
with nothing but hostility. I have not once insulted any of you, yet all you
have done is insult me. To dispute the presence of deep nulls that occupy a
small area shows how truly ignorant you are of acoustics. Empirical evidence
trumps theory every time, but you're obviously too important to be bothered
with a test as simple as I have described. My earlier report proves beyond
all doubt that such deep and confined nulls do in fact exist.

That someone with your apparent education doesn't understand how
fundamentally important bass traps and other acoustic treatment are to
control rooms and home theaters is truly staggering. This is not the first
time dumb ol' uneducated me had to explain the basics to an egghead with a
wall full of degrees. Take a moment to look in the mirror, and bring a
napkin, because you have egg all over your face.

When you are willing to discuss the issues without resorting to childish
name calling if someone disagrees, please let me know.

--Ethan

Stewart,

Shouldn't this post be headed 'advertorial'?

Yet again you present a post that fails to address even one of the issues,
opting instead just to insult me.

The ignorant and mean-spirited replies in this group is amazing.

--Ethan

"Ethan Winer" ethan at ethanwiner dot com wrote in message
...
Your address appears valid so I'll send you that via email. I'm
not
comfortable dragging his name into this publicly.

Might be valid but it isn't mine. I don't let my email out into
the wild.

Just post his company's name. We can look up his peer-reviewed
journal papers, conference publications, and patents.

fixes room problems, and part of that is to reverse the peaks
and nulls, why
do you criticize that explanation? And besides, that wasn't
even meant as a

First, because it's technically inaccurate on how the process
fundamentally works. Although, I agree he could have gave the
laymans explaination to you. Second, because the claim was made
that it's only valid for a small listening area...which is not
true for advanced techniques.

"grand explanation" of deconvolution anyway. It was just a way
to explain
the trade-off between correcting a tiny part of a room
perfectly or a larger
area less completely. Again, act like a human being and give me
a freakin'
break. Instead of attacking me or Bill, why don't you address
the actual
issues?

Because that trade-off only applies to the most simplistic,
elementary implementation. An expert in the field would know
this.

I have no idea. Bill mentioned that one of his systems uses
eight speakers
and eight mikes. The systems he designs are not meant for room
correction in
hi-fi listening rooms, though they're related closely enough to
use
identical technology.

Then he should be familiar with wide area correction techniques.

If he were indeed an expert in all things wave he'd be
laughing at the
concept of Bass Traps. Decpetive marketing at best. Snake oil
at worst.

That's an astounding statement from someone who claims to be an
audio
professional.

I made no such claim of being an audio professional.

The idea that a Bass Trap stuck in a corner can tame low
frequency room modes is laughable. I agree acoustic treatments
can be necessary and can have exceptional results. But how can a
small broadband absorber help room modes?

For example, let's say I have two axial room modes creating
audible peaks at 21 and 26 Hz. What would you suggest?

On Sat, 13 Sep 2003 16:12:25 -0400, "Ethan Winer" ethan at ethanwiner
dot com wrote:

Stewart,

Shouldn't this post be headed 'advertorial'?

Yet again you present a post that fails to address even one of the issues,

My post *exactly* addressed the main issue - you are a snake-oil
merchant, selling band-aids for broken bones.

opting instead just to insult me.

The ignorant and mean-spirited replies in this group is amazing.

You insult yourself by posting ignorant rubbish, such as that bass
frequencies 'focus in a corner'. This is arrant nonsense, as are 'bass
traps' which are less than a significant fraction of the room volume.
You won't find any of your snake-oil toys in serious recording
studios.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article ,
Ethan Winer ethan at ethanwiner dot com wrote:
Who said anything about only one absorber or their being small? The most
popular panels we sell are 2x4 feet and we typically recommend eight for a
normal home-sized room. Friday I supervised installing a set of our traps in
the home studio of a famous record producer. The room is about 13x20 feet
with a vaulted ceiling, and we used ten panels. I'll add that the producer's
engineer was thrilled with the improvement these ten traps made, and before
we left he was emailing a friend at a big-name studio about how cool our
stuff is. I'm not saying this to brag! Just to make the point that THIS is
how real-world acoustics problems are solved.

So you are passing off paraphrased testimonials with no
quantified results from unnamed people who as some "proof?"

Please, why not SHOW us what happened to the 1/3 octave RT60
time as a result of your fabuluous treatments?

Your "walk around the room" measurements show the level of
amateurish stunts you call "measurements."


--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

Dick,

your assertion of HUGE chages in SPL over a distance of 4 inches still
constitutes an extraordinary claim that contradicts the behavior of waves.

That is the essense of my "egg on your face" comment. When you take the time
to play some LF sine waves and walk slowly toward and away from the walls
looking for nulls, you will immediately see that I am right.

your assertion blindly assumes that the room will be excited modally in
essentially the same manner at 100 Hz that it is excited at 70 Hz

Actually, modal excitation has nothing to do with this. The mechanism is
basic acoustic interference due to reflections at the room boundaries. See
this article by studio designer Wes Lachot, which explains the phenomenon in
detail:

www.recording.org/users/acoustics/waves_wl.html

No, I have not, because I know form both theory and experience

Refusing to try this simple test is pretty arrogant. Especially since I am
handing you the proof on a silver platter! As I said elsewhere, empirical
evidence trumps theory every time. Not that the established theory is wrong!
Just that you appear not to understand it. Which is okay because a LOT of
otherwise knowledgeable folks don't understand this phenomenon.

You cannot get good data "in only a few minutes."

Maybe not, but that's all it would take for you to learn that I am right
about big changes in level over very small distances.

You simply CANNOT "focus" a wave whose wavelength is

So now you're disputing that bass traps work best when mounted in the room
corners?

EW: and you can absorb more than the equivalent surface area would
indicate.

RP: An extraordinary assertioon, now prove it.

See "The numbers game" on the MiniTraps page at my company's site:

www.realtraps.com

Hint: Spacing an absorbing panel away from a surface, or mounting it
straddling a corner, lets sound waves enter from the rear. This way both the
front and rear surfaces absorb, which yields absorption coefficients
substantially greater than 1.0.

A chamber having a constant RT60 time across the bandwidth with perfectly
reflecting walls will have a perfectly flat response.

It would except for the pesky acoustic interference explained in Wes
Lachot's article linked above.

This is not proof, this is self-promoting testimonial.

So now you're disputing we have satisfied customers?

Your earlier "report" is nothing of the kind, it is a collection of
assertions, reassertions and rereassertions and contains NO data of
substance.

I stated the measured results of my tests. Apparently you think I'm too
incompetent to even connect a microphone to a voltmeter and read some
numbers! :-)

I can take insults and abuse. It's not a problem because I have no ego with
this stuff. I just enjoy talking shop. I wouldn't be surprised if you and I
even became friends eventually. Stop by my company's booth at the AES show
and say Hi. I'd like to meet you in person, and I'm sure I could learn a lot
from you. In the mean time, please take a few moments to play the sine
waves. It will be a real eye-opener for you.

--Ethan

Ethan Winer wrote:

Dick,

So you are passing off paraphrased testimonials with no quantified results
from unnamed people who as some "proof?" Please, why not SHOW us what
happened to the 1/3 octave RT60 time as a result of your fabuluous
treatments?

Not to discount science, but it matters little how the rt60 changed when the
customer is thrilled with the results!

It may matter little to you and your customer, but it matters a lot in
the context of this discussion. The issue here is whether or not there
is OBJECTIVE, VERIFIABLE evidence that either traps or DSP provide
practical solutions for certain room acoustic problems. Thus simply
asserting that "it sounded good" don't cut it.

I'll have to side with Dick on this one. Besides, if your devices really
do work as well as you say they do, then, in all seriousness, you have
nothing to fear from science.
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% % 'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr

On Sun, 14 Sep 2003 12:29:39 -0400, "Ethan Winer" ethan at ethanwiner
dot com wrote:

Dick,

So you are passing off paraphrased testimonials with no quantified results
from unnamed people who as some "proof?" Please, why not SHOW us what
happened to the 1/3 octave RT60 time as a result of your fabuluous
treatments?

Not to discount science, but it matters little how the rt60 changed when the
customer is thrilled with the results!

Thus spake all peddlers of snake oil...................

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Stew,

You are an ignorant idiot.

Thanks, though I still think you're a cool guy.

The first is fixable, the second is not.

First and second what?

Are you now disputing that spacing an absorber panel away from the wall lets
sound enter the rear to obtain an absorption coefficient great than 1.0?

Do you know anything at all about acoustics? You certainly seem to be
struggling with even the most basic concepts.

So does George Cardas. His products are also purest snake oil.

Okay, you got me there. I actually had the same thought after posting
yesterday, that lots of homeopaths and astrologers etc. must have satisfied
customers. Hopefully the level of folks I deal with can tell the difference
between a placebo and the improvement real acoustic treatment make in their
rooms.

--Ethan

Now although I've been watching the thread, it hasn't been too intensely, and a
number of people have been quoting quite a range of conditions. Some seem to say
categorically that it's impossible to get frequency response variations of more
than 15dB, and there also seems to be a consensus here that moving 8 degrees
along a wave cannot possibly alter the amplitude. Of course if you accept the
first, then the second is true too. Oh that it WERE true - then many of my past
headaches simply wouldn't have happened. But in the real world it's quite common
in an untreated studio to measure pure tone variations much greater than 15dB.
And when there is a genuine cancellation notch, moving 8 degrees away from it is
enough to make a substantial difference - taking the simplest case of 2 waves
traveling in opposite directions, if they cancel at one point, then 8 degrees
away the waves will actually be 16 degrees different in phase, or about 12dB
below a single wave's full amplitude.

I can only assume that most of the posters either measure frequency response by
third-octaves (not very relevant for this discussion), and/or have never visited
an untreated studio. But even so, it really is time to "give a guy a break".

On Sun, 14 Sep 2003 15:04:19 +0000 (UTC), (Richard D
Pierce) wrote:

In article ,
Ethan Winer ethan at ethanwiner dot com wrote:
Richard,

Your assertion that such variation occurs over a distance of 4 inches or
7.4 degrees is an extraordinary claim contrary to the behavior of waves.

I measured 100 Hz, not 70, but I'm sure the results will be similar at 70
Hz.

The wavelength at STP at 100 Hz is 11.3 feet, 4 inches
corresponds to a phase difference of 8 degrees. \

Yes, you're ight, the results will be similar, your assertion of
HUGE chages in SPL over a distance of 4 inches still constitutes
an extraordinary claim that contradicts the behavior of waves.
Further, your assertion blindly assumes that the room will be
excited modally in essentially the same manner at 100 Hz that it
is excited at 70 Hz, a furtjher extraordinary claim.

So you're still disputing my *measured* response variations?

Yes, indeed I am, because...

Have you
never played a sine wave in a room and walked around?

No, I have not, because I know form both theory and experience
that this is a perfectly sloppy, LOUSY and highly inaccurate
way of measuring the acoustic field in an enclosed space. This
fact is WELL known to acousticians abd professional
practitioners in the field and has been known as being a poor
way of measuring for DECADES. The problems have been described
by the likes of Beranek (c.f. Acoustics), Kinsler and Frey
(Fundamental of Acoustics) and many others.

However, you implication that I have never done measurements of
acoustic fields in spaces is either highly uninformed
speculation or outright dishonesty. I have made MANY such
measurements over the last 30 years, but using FAR more precise,
dependable techniques that suffer from far less operator-induced
intrinsic errors than your casual walk-around-the-room "method"
has.

It only takes a few minutes.

And this statement alone tells us your lack of experience in the
field. You cannot get good data "in only a few minutes."

explain to us how a trap which takes up very small percentage of the total
surface area of a reflecting surface can change the effective absorbtion
coefficient of that surface by any more than a small percentage?

Sure, easy. Bass traps work best in the room corners. Put them there, where
the bass frequencies focus,

This is yet another statement that illustrates quite clearly you
do not understand the fundamental physics of acoustics. You
simply CANNOT "focus" a wave whose wavelength is proximal to the
dimensions of the structure. Interference, simply bulk
absorbtion, reflection and diffraction completely dominate the
behavior of waves. The structiure must be MANY times the size of
a wavelength before even crude focusing takes place.

and you can absorb more than the equivalent
surface area would indicate.

An extraordinary assertioon, now prove it.

Do a dozen bass traps in a room solve all problems? No, of course not. You'd
have to cover literally every surface with material that's 100% absorbent at
all frequencies to achieve a perfectly flat response.

Again, another statement that, all by itself, illustrates the
significant flaws in your models. A chamber having a constant
RT60 time across the bandwidth with perfectly reflecting walls
will have a perfectly flat response.

This is maybe one reason why "bass traps" are NOT used by professional
acoustic engineers in real acoustic situations

Tell that to all the professional recording engineers who love our products!

This is not proof, this is self-promoting testimonial.

if the data YOU presented about YOUR treated room is ANY indication, then
it does a LOUSY job.

I have tried hard to engage in a meaningful discussion, and have been met
with nothing but hostility. I have not once insulted any of you, yet all you
have done is insult me. To dispute the presence of deep nulls that occupy a
small area shows how truly ignorant you are of acoustics. Empirical evidence
trumps theory every time, but you're obviously too important to be bothered
with a test as simple as I have described. My earlier report proves beyond
all doubt that such deep and confined nulls do in fact exist.

Your earlier "report" is nothing of the kind, it is a collection
of assertions, reassertions and rereassertions and contains NO
data of substance.

Regards,
Tony (remove "_" from email address to reply)

In article ,
Tony Roe wrote:

Now although I've been watching the thread, it hasn't been too
intensely, and a number of people have been quoting quite a
range of conditions. Some seem to say categorically that it's
impossible to get frequency response variations of more than
15dB,

NOBODY EVER said that, Mr. Roe, nobody.

and there also seems to be a consensus here that moving 8
degrees along a wave cannot possibly alter the amplitude.

NOBODY EVER said that, Mr. Roe, nobody.

The claim was made of VERY LARGE amplitude variations over small
distances, in the range of 1-4 inches, at low frequencies, in
the realm of 70-100 Hz.

I wish people would PLEASE represent what people say accurately.

Of course if you accept the
first, then the second is true too.

Since NO ONE said either the first or second, the remainder of
your discussion is irrelevant, no?

Why do you choose to completely misrepresent what someone else
has said?

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

In article ,
Ethan Winer ethan at ethanwiner dot com wrote:
Randy,

The issue here is whether or not there is OBJECTIVE, VERIFIABLE evidence
that either traps or DSP provide practical solutions for certain room
acoustic problems.

Of course. Apparently you don't realize that our MiniTraps and other
products have been tested in a certified acoustics lab (IBM's lab in
Poughkeepsie, NY),

Please show us, then, the certification documentation.

The MiniTraps have also been fire tested.

So, you have obtained UL approval? Under what UL number? If you
have, that would be a good thing for people to know about.

If not, it would be a bad thing to make the claim without the
recognized certification.

To date, other then more and more claims, you have provided
NOTHING to substantiate any of your claims. You have admitted
knowing nothing about the relevant DSP techniques, yet criticize
the techniques you know nothing about. You have provided NO
substantiation of your claims, but instead have chosen to
provide "testimonials" without even saying who they alledgedly
came from. You have given us only the vaguest summaries of
"measurements" described, by your self, as the most informal and
innacurate sort with no dependabuility at all. You have chosen
to ignore any number of well accepted, well understood and
commonly used standards for acoustics measurements. You have
made wild and, regrettably preposterous claims about "focusing
waves into corners" and the like.

What are we to think, sir?

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

Dick,

Please show us, then, the certification documentation.

Man, is this ever a tough crowd! :-)

Here's a scan of the official test report on IBM's stationary:

www.ethanwiner.com/misc-content/IBM-Mini.gif

The data on our site is derived from this table, but formatted for
appearance and to show a comparison of other popular but less effective
products. You'll notice that the scan linked above has one column blanked
out, which is the test data for a competing product. That absorber measured
only 3/4 as effective as the vendor claims, but our site shows their
(overstated) published specs anyway because our MiniTraps are so far
superior it doesn't matter.

So, you have obtained UL approval? Under what UL number? If you have, that
would be a good thing for people to know about.

That's why I mentioned it. A scan of the report from the certified testing
lab is on our site, and this is a direct link you can click from he

www.realtraps.com/mini_fire.gif

To date, other then more and more claims, you have provided NOTHING to
substantiate any of your claims.

What claims? That a 100 Hz tone can vary by 15 dB across a span of four
inches? Please read this carefully: What more proof can I offer than to tell
you to try it? What words could I possibly say to convince you that this
phenomenon is not only possible, but typical? For two weeks now I have
repeatedly asked you to play tones and walk around. You have refused. What
more could I possibly say or do? As soon as you try this test you will see
that I am correct.

You have admitted knowing nothing about the relevant DSP techniques

I don't know the higher math, but to paraphrase you, I know what is and what
isn't possible. For the 17th time, I'm still waiting for either a solid
number of how large an area DSP can correct and by how much, or the name of
a showroom where I can hear such a system. A price tag would help too, so I
can assess for myself if it's really a practical and affordable solution.
This is the real issue and, again, you have evaded it for weeks now.

You have chosen to ignore any number of well accepted, well understood and
commonly used standards for acoustics measurements.

Then let's discuss it. What accepted standards have I ignored? I think I
have a pretty good handle on how acoustic absorbers are measured - see the
tutorial on our site - and I know very well the failings of some of the
common methods.

--Ethan

Tony,

in the real world it's quite common

Thanks for confirming. I can see why Richard & Co. don't believe this occurs
because it's not intuitive. I've had this same discussion with others
several times in the past. This thread mimics one from a few months ago in
the Home Theater Builder forum where an "expert" home theater designer
argued with me for three weeks about the presence of deep nulls at non-modal
frequencies. Like Dick, he refused to try the sine wave test because he just
"knew" I wasn't right. Then one by one others in the forum tried it and
reported their results. I've been trying to spare Dick the embarrassment
that other fellow endured. If only Dick would try it we could get past this
and on to more interesting matters...

I can only assume that most of the posters either measure frequency
response by third-octaves (not very relevant for this discussion)

Yes, this is a big limitation with 1/3 octave testing. The main problem is
that a third of an octave is far too coarse to see what's really happening.
A typical room has many peaks and nulls throughout the bass range, and it's
common for a peak and its adjacent null to both fall within the same 1/3
octave band. So the average reading for the entire band is nice and flat,
even though the response really varies by 15 or more dB!

--Ethan

Rusty Boudreaux wrote:

"George Deliz" wrote in
message
This sounds very interesting. How is this done in practice?
Are there products available that would allow an audiophile to
do this
and about how much would it cost?

I'm not aware of any commercial solution for the audiophile
market. The signal processing details are way beyond the
capabilities of the typical high-end company. This is hard
science, not snake oil. Since the audiophile market is so tiny I
bet we won't see this in consumer applications until mainstream
receivers support it via an ASIC or chipset developed elsewhere.

Apparently, there is no DSP solution commercially available at any
price.
Therefore, there is no DSP solution. If such a solution were to be
developed, what would be required, in addition to the DSP
hardware/software? Would more speakers be needed? Would massive amounts
of amplifier power be needed to fill in dips? Inquiring minds want to
know.
The theory behind the process has been explained but no one here has yet
provided a description of what a practical implementation would require.


George Deliz

Richard D Pierce wrote:

In article ,
Rusty Boudreaux wrote:
"George Deliz" wrote in
message
This sounds very interesting. How is this done in practice?
Are there products available that would allow an audiophile to
do this
and about how much would it cost?

I'm not aware of any commercial solution for the audiophile
market. The signal processing details are way beyond the
capabilities of the typical high-end company. This is hard
science, not snake oil. Since the audiophile market is so tiny I
bet we won't see this in consumer applications until mainstream
receivers support it via an ASIC or chipset developed elsewhere.

This is an important point that bears repeating. The total
audiophile market is SO tiny that any company with the financial
wherewithall to do heavy DSP development would not even notice
if the high-end market were to suddenly vanish without a trace.
The size of this market combined with the utter irrational
insanity of it along with its volatility makes it unattractive
for any serious development effort. Basically why should a
company bother trying to cater to a segment that might,
altogether, make up 1% of its potential business yet cost it
tens times it in the trouble it would generate?

There is no innovation in the high-end to speak of, there's
little real development of any sort, there's no scholarly
research, just blind and stumbling intuition, snake oil, magic
arts and mythology.


Why should we expect the high-end boutique companies to develop this
technology.
I would expect the likes of Sony or Harman International to lead the way
if a practical implementation were possible. A feature that compensates
for less than ideal room acoustics should be a good selling point in
surround sound receivers and processors.

George Deliz

Ethan Winer wrote:

Tony,

but only at one point at a time

Thanks. This has been my point all along. I'm a seat of the pants kind of
guy that looks for practical solutions to real problems. This ain't it.


Even if a DSP room correction scheme could do no better than correct for
a single listening location, it would still be preferable to room
treatments for the vast majority of stereo and home theater owners who,
like myself, are unwilling to alter the decor of their rooms. As has
been pointed out here, the hard core audiophile is a tiny minority. Most
people who will be buying home theater components will not be willing to
bolt acoustic panels to their walls or even put down otherwise
unnecessary rugs. They will want to be able to just hook up the stuff
and go. If DSP can make the end result better sounding then I'm all for
it, but I'm not going to hold my breath waiting for products to appear.

George Deliz

George,

Your points here and elsewhere are good ones. If nobody makes any DSP
solution, let alone one that actually works, then the whole idea is
irrelevant.

Most people who will be buying home theater components will not be willing
to bolt acoustic panels to their walls

Hey, I had no problem convincing my wife. :-)

Seriously, you are correct that most acoustic treatment is visually
intrusive. REALLY high end rooms have plenty of treatment, but it's hidden
behind fancy fabric stretched over the walls. High end recording studios do
likewise, with lots and lots of fiberglass built into the soffits, placed
above openings near the wall/ceiling corners, and behind fabric stretched
over the walls. Smaller studio owners don't have million dollar budgets, but
the smart ones realize they need to treate their rooms and do so regardless
of how it looks. Not that acoustic panels have to be ugly!

Years ago spouses objected to big speakers and big racks full of cool gear.
Today these things are more accepted. When the sound quality is important
enough to spend $5 grand or more on big speakers, big screens, and other
gear that shows, then $1,000 worth of acoustic treatment could be acceptable
too. And those that care more about appearance than sound will just have to
put up with echoes and muddy bass. As Scotty says, "I canna change the laws
of physics."

--Ethan

"Stewart Pinkerton" wrote in message
...
So does George Cardas. His products are also purest snake oil.

Not true, *real* snake oil does have some uses.

TonyP.

On Mon, 15 Sep 2003 14:14:45 -0400, "Ethan Winer" ethan at ethanwiner
dot com wrote:

Stewart,

Thanks for the confirmation! Ignorance is fixable by the supply of
information, and inability to comprehend the information is more of a
problem.

I still have no idea what you're referring to. First and second what?

At this point, it seems advisable to stop teaching the hog to sing....
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Mon, 15 Sep 2003 13:52:31 -0400, "Ethan Winer" ethan at ethanwiner
dot com wrote:

Stewart,

I have certainly never measured more than 10dB in a normal domestic living
room.

How did you measure, with sine waves or pink noise?

Both.

I can see you haven't tried the sine wave test either...

Why? Because I don't agree with your claims that support your sales
campaign?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 16 Sep 2003 13:49:57 +1000, "Tony Pearce"
wrote:


"Stewart Pinkerton" wrote in message
...
So does George Cardas. His products are also purest snake oil.

Not true, *real* snake oil does have some uses.

Aw, be fair now, George's $10,000 cables *do* work just as well as $5
Rat Shack specials.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
...
I still have no idea what you're referring to. First and
second what?

At this point, it seems advisable to stop teaching the hog to
sing....

Yeah, I've given up, too. It's kinda sad. I like a good
technical debate that raises the bar of knowledge but it's clear
that isn't happening in this thread. I'm tired of banging my
head against the wall.

Stewart,

Because I don't agree with your claims that support your sales campaign?

No, because if you had played sine waves and walked around *slowly and
carefully* you'd know I am right!

At this point, it seems advisable to stop teaching the hog to sing

That pretty well sums up my hope to ever get through to you too.

For a group of guys that claim to enjoy technical issues, this sure has been
one-sided. I spent two hours looking through the references you linked, I
did some further searching of my own, and spent half an hour discussing this
with my DSP expert friend. You guys, on the other hand, can't be bothered to
play a 100 Hz tone for 2 minutes while you walk toward and away from the
walls.

At this point I have to assume you did try sine waves, realized I'm right,
and are now saying you're "tired of this" as a way to save face. Yes?

--Ethan

On Tue, 16 Sep 2003 09:58:22 -0400, "Ethan Winer" ethan at ethanwiner
dot com wrote:

Stewart,

Because I don't agree with your claims that support your sales campaign?

No, because if you had played sine waves and walked around *slowly and
carefully* you'd know I am right!

I have done. In my room, you're wrong. You can see my room at
http://www.apah69.dsl.pipex.com/

At this point, it seems advisable to stop teaching the hog to sing

That pretty well sums up my hope to ever get through to you too.

Sorry, I will keep insisting that 2+2=4............

For a group of guys that claim to enjoy technical issues, this sure has been
one-sided. I spent two hours looking through the references you linked, I
did some further searching of my own, and spent half an hour discussing this
with my DSP expert friend. You guys, on the other hand, can't be bothered to
play a 100 Hz tone for 2 minutes while you walk toward and away from the
walls.

As Dick has pointed out, your first mistake is in thinking that you
can characterise a room in a couple of minutes.

At this point I have to assume you did try sine waves, realized I'm right,
and are now saying you're "tired of this" as a way to save face. Yes?

No. I'm tired of trying to explain basics to someone who sells
acoustic bandaids.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article ,
Ethan Winer ethan at ethanwiner dot com wrote:
Stewart,

Because I don't agree with your claims that support your sales campaign?

No, because if you had played sine waves and walked around *slowly and
carefully* you'd know I am right!

At this point, it seems advisable to stop teaching the hog to sing

That pretty well sums up my hope to ever get through to you too.

For a group of guys that claim to enjoy technical issues, this sure has been
one-sided. I spent two hours looking through the references you linked, I
did some further searching of my own, and spent half an hour discussing this
with my DSP expert friend. You guys, on the other hand, can't be bothered to
play a 100 Hz tone for 2 minutes while you walk toward and away from the
walls.

Because playing a 100 Hz tone while walking around with some
unknown sound level meter completely ignoring all the
measurement errors your sloppy techniques introduce without at
all understanding the most fundmanetal of acoustical prinsiples
is not the way anyone, except you, seems to do things.

At this point I have to assume you did try sine waves, realized I'm right,
and are now saying you're "tired of this" as a way to save face. Yes?

No.

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

Stewart,

I have done. In my room, you're wrong.

Let's see, your room is 25x18 feet with an 8-9 foot ceiling, and all the
surrounding surfaces are either brick, similarly massive, or 3-layer glass.
And you have played low frequency sine waves yet never noticed severe nulls
at 1/4 wavelength (and its odd multiples) away from the room boundaries. You
are either very lucky, very unobservant, or as hel@40th suggests, deaf.

Sorry, I will keep insisting that 2+2=4

2+2 does indeed always equal 4. The problem is you don't seem to understand
the "2" part!

Here's a quote for you that's probably relevant he

"All great truths begin as blasphemies." --George Bernard Shaw

--Ethan

In article ,
Ethan Winer ethan at ethanwiner dot com wrote:
Dick,

Because playing a 100 Hz tone while walking around with some unknown sound
level meter completely ignoring all the measurement errors your sloppy
techniques introduce

What's wrong with the way I measured? I played a 100 Hz tone, positioned the
mike until the record level meter read the minimum, and then swung the mike
stand four inches to one side and read the meter again. Why is that not
valid?

You said "you played a 100 Hz tone and walked around the room."

Which is it, Mr. Winer? walked around the room, or swung the
mike stand 4 inches to and fro?

Which is it, Mr. Winer, 100 Hz or 70 Hz?

Which is it, Mr. Winer, 1 inch or four inches?

Your data is inconsistent, your techniques are sloppy, your
claims are vague and all over the map.

Until such time as you put the effort into educating yourself on
the proepr measurement techniques (c.f. Beranek et al), and
understand the sources of error, your data is simply not to be
trusted. Beyond that, you CLEARLY have a commercial axe to
grind, I don't.

Your comment earlier that "what does it matter what the RT60
time is if the customer is happy," can, by simple reductio ad
absurdum, end up saying, "what difference does ANY measurement
mean", and here you present us with measurements and expect us
to accept them.

Absolutely NO insult is or was ever intended, but in all
honesty, your measurement techniques by your own description are
VERY sloppy, unsystematic and the resulting data IS unreliable.
Measuring the distribution of energy in a room is difficult to
do correctly and completely and CANNOT be done by "walking
around the room for a couple of minutes while playing sine
waves." You might think so, you might fervently believe so, but
you are wrong, I am sorry to say. I have been doing just these
sorts of measurement for over a quarter of a century, and 25
years ago, I was doing precisley the same sloppy, uncontrolled,
highly error-prone measurement YOU were doing and finally
learned how unreliable they were.

So, Mr. Winer, to answer your question again, yes, I HAVE done
such measurements, and I learned a LONG time ago how unreliable
they are. That's why, when I have to determine the energy
distribution in an enclosed space I DO NOT use the technique you
favor, because I and MANY other practioners in the field know of
the problems it has.


--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

Dick,

Which is it, Mr. Winer? walked around the room, or swung the mike stand 4
inches to and fro?

If you read my report above you'll see that I played 100 Hz, walked around
to find the deepest null, put the mike there, measured the level, swung it
four inches away, and measured again. Nothing sloppy about that!

I have been doing just these sorts of measurement for over a quarter of a
century

Apparently you have not been measuring the right things.

when I have to determine the energy distribution in an enclosed space I DO
NOT use the technique you favor

Who said anything about energy distribution? You said it's not possible for
100 Hz to vary by 15 dB across a span of four inches, and I have proven
beyond all doubt that it can and does.

Absolutely NO insult is or was ever intended

Same here. But you are very wrong, and it's obvious I'll never convince you
of that other than getting you to visit my studio so you can watch the
measurement yourself. And yes, that absolutely is an invitation! Even easier
for you, what say I come up and visit you some weekend, and show you this
phenomenon in your own room. Deal?

--Ethan

Richard D Pierce wrote:
[...]
Measuring the distribution of energy in a room is difficult to
do correctly and completely and CANNOT be done by "walking
around the room for a couple of minutes while playing sine
waves." You might think so, you might fervently believe so, but
you are wrong, I am sorry to say. I have been doing just these
sorts of measurement for over a quarter of a century, and 25
years ago, I was doing precisley the same sloppy, uncontrolled,
highly error-prone measurement YOU were doing and finally
learned how unreliable they were.

So, Mr. Winer, to answer your question again, yes, I HAVE done
such measurements, and I learned a LONG time ago how unreliable
they are. That's why, when I have to determine the energy
distribution in an enclosed space I DO NOT use the technique you
favor, because I and MANY other practioners in the field know of
the problems it has.

Dick,

I have a couple of points/questions on this subject that have
surfaced during this thread:

1. For the moment let's consider the process of measuring the room
response resulting from one speaker in a room. You would theoretically
have an uncountably infinite number of system functions, one from the
speaker to each position (x,y,z) in the room, so the room response
would be H(x,y,z,w), where w = 2*pi*f and f is frequency.

Ah, but at any one (x,y,z), a listener does not perceive H(x,y,z,w),
does he? Would, rather, he perceive He(phi, rho, w) * H(x,y,z,w),
where e = r or l, and He(rho, phi, w) is the frequency response of the
left or right ear that is positioned at (x,y,z) and oriented at an
azimuth rho and an elevation phi. No?

Similarly, your sound pressure level meter with a microphone and
enclosure would have a system function of Hm(rho, phi, w). No?

In general, Hm(rho, phi, w) is not equal to He(rho, phi, w), is it?
That is, if you put the SPL meter at position (x,y,z), you won't
necessarily measure the same thing your ears would hear at position
(x,y,z), would you?

Actually, I can see where this model is still inaccurate. He(rho, phi, w)
is only valid assume the sound comes from a certain direction. To get
the entire picture, you'd have to have a 3-D spatial response at (x,y,z)
for H() (from the spaker) and then sum the contributions from all
directions. So you'd need H(x,y,z,rho,phi,w) and then compute

\int\int H(x,y,z,rho,phi,w) He(rho,phi,w) d rho d phi.

Right?

2. Would it not be possible for the system response H(x,y,z,rho,phi,w) to
change drastically at any frequency with only a slight change in (x,y,z)?
As an extreme example, let's say we measured at (x,y,z) that was at the
inside surface of a 1-inch-thigh steel wall (part of a strange listening
room); then we moved 1.5 inches in and measured at (x+x0, y+y0, z+zo).
The frequency response would then drastically change for just a small change
in position, even for low frequencies. No?
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% % 'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr

Randy Yates wrote:
inside surface of a 1-inch-thigh steel wall (part of a strange listening

I meant to write "1-inch-thick".

room); then we moved 1.5 inches in and measured at (x+x0, y+y0, z+zo).
The frequency response would then drastically change for just a small change
in position, even for low frequencies. No?

The point is, even though a vector sum of low frequency waves
doesn't change much when moving through a small fraction of
a wavelength, might you not still get a big variation when
moving through a small fraction of a wavelength if, during
that movement, the system response changed at that frequency
due to the position-dependent spatial properties of the room?
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% % 'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr

Randy Yates wrote:
[...]
Actually, I can see where this model is still inaccurate. He(rho, phi, w)
is only valid assume the sound comes from a certain direction. To get
the entire picture, you'd have to have a 3-D spatial response at (x,y,z)
for H() (from the spaker) and then sum the contributions from all
directions. So you'd need H(x,y,z,rho,phi,w) and then compute

\int\int H(x,y,z,rho,phi,w) He(rho,phi,w) d rho d phi.

Actually, this He(rho,phi,w) is not the same one as I mentioned
a few lines earlier. This one is the response of your ear, given
your head is in a fixed orientation, to sound coming at an angle
of (rho, phi).
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% % 'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr